One cause of lower back pain is stress across the sacroiliac joint. Sacroiliac joint fusion can relieve stress on the sacroiliac joint by stabilizing the sacrum and ilium to one another via one or more implants, such as screws. These conventional implants pass laterally across the joint and prevent relative movement between the bones.
Conventionally, implanting such devices to fuse the sacrum and ilium has included drilling through the sacrum and ilium, using a tap assembly to create threading, and then inserting a threaded screw through the joint and across both bones. Other implants include inserting titanium wedges across the joint. This technique involves drilling through a threaded pin and then using a shaped broach to create the shape of the implant. The implant is then tamped through the joint. Thereafter, bone fusion can occur around the implants. In some cases, bone grafting material can be packed into or around the implant to promote bone fusion.
In order to insert such implant screws, often a pointed-tip screw is attached to a driving shaft, and is inserted to the appropriate depth to hold the bones in a fixed spatial relationship. Some conventional insert screws also have passages through which bone grafting material can be either packed prior to insertion, or routed during or shortly after the screw is placed in the bone. After the implant is placed, discomfort or injury can be caused by the sharp tip of the screw being near the sacral foramina.